1. Field of the Invention
The present invention relates to a manufacturing method and a hermetic glass-to-metal seal for a circuit component such as liquid electrolytic capacitor.
2. Description of the Prior Art
A conventional insulated sealing material for a liquid electrolytic capacitor employs a gasket made of rubber or synthetic resin. This gasket does not provide gas tight performance, although it accomplishes the sealing effect when squeezed by the cathode case. Therefore, there is a possibility that the electrolyte will leak, causing a reduction in the capacitance of the capacitor, and there is also the possibility the escaped electrolyte will corrode the parts around the capacitor.
For a dry-type electrolytic capacitor, hermetic glass-to-metal seal is employed. For example, in U.S. Pat. No. 3,669,698, binder is added to the raw material glass powder. A bead is prepared by the calcination of the above-mentioned mixture after it is mixed homogeneously, pressed to a certain form and then dried to volatilize the solvent in the binder.
The bead, mentioned above, is set into an opening of a member which composes the capacitor, and fused with a longitudinal conductor so arranged that it pierces through the bead. In this prior art, suspended dust in the air is apt to contaminate the bead since the prior art method involves a lot of steps. Moreover, there is a possibility that the added binder for forming a bead does not volatilize entirely during the calcination and remains in the glass. The binder remaining in the glass may cause a phase separation of the glass and the melting glass is not apt to flow. Therefore there is a possibility that the contact condition between the glass and the metallic member or longitudinal conductor becomes imperfect so that the glass cracks.
It is an object of the invention to provide a manufacturing method and a hermetic glass-to-metal seal which employs glass including no undesirable impurities so as to accomplish a perfect sealing.
It is another object of the invention to provide a manufacturing method for a hermetic glass-to-metal seal which is very simple.
For a better understanding of the present invention, together with other objects, reference is made to the following description, taken in conjunction with the accompanying drawings.